The invention relates to the purification and separation of oil, water and solids from waste oil. This waste oil can be found in many forms and is particularly found in large quantities as storage tank bottoms and in lagoons where waste oil has historically been transferred for storage. Crude oil contains varying, but in some cases high, percentages of B.S. and W., i.e., bottom sediment and water, plus paraffin and other materials. These contaminates adhere to the sides and build up on the bottom of crude oil storage tanks, forming a thick, viscous slurry referred to as waste tank bottom sludge or bottom settlings and water. This build-up of water, paraffin, sand, clay, and other materials is generally rich in hydrocarbon content, but unsuitable for refining. These circumstances result in reduced storage capacity for the crude oil tanks and many millions of barrels of nonuseable crude product.
Among other things, tank bottom sludge is characterized by high concentrations of inorganic contaminants, e.g., inorganic salts and heavy metals (sodium, calcium, vanadium, nickel, chromium, etc.). These affect the expensive catalysts used in the refining process making such waste oil unsuitable for refining even after it has been separated from any water and solids.
Much of the mineral oil (petroleum) which is produced in various countries of the world contains at least some water and at least some finely divided solid components. If the oil itself as extracted from the earth as a crude does not have such solids and water present, then scales, salts and dirts from oil well field equipment, pipelines, tankers, tanks and other sources introduce water and solids into the oil. In conventional processes for breaking petroleum emulsions the mineral oil is separated for use in refineries and the water is separated for reuse or disposal. There is a tendency, however, for the more difficult to break portions to be concentrated without separation. In the past, the discard streams from refineries which contain the more difficult to treat suspension-emulsion fractions and tank bottom sediments have been collected and trucked to disposal lagoons or other locations where the material could be discarded. This is an economic waste and an ecological disaster. A major refinery may have tens of thousands of pounds per day of such emulsion-suspensions which because of new environmental regulations are now not acceptable for solid waste disposal and which are not acceptably left in waste lagoons where the mixture would represent a long-term environmental hazard.